1. Field of the Invention
The present invention relates to a method of multi-stage substrate etching and a terahertz oscillator manufactured using the same method, and more particularly to a method of multi-stage substrate etching in which a first substrate is etched to a desired depth, a second substrate previously etched to a certain depth is bonded to the first substrate such that the etched surface thereof faces the first substrate, and finally the second substrate is etched again to thereby form a step structure, and a terahertz oscillator manufactured using the same method.
2. Description of the Prior Art
A terahertz band is very important with respect to applications of molecular optics, biological physics, medical science, spectroscopy, image processing appliances, and security appliances. Nevertheless the importance of the terahertz band ranged between an existing microwave band and optical frequency, it is true that there is few currently developed oscillator or amplifier using the same band due to various physical, engineering limitations. Recently, such a terahertz band oscillator or amplifier has been developed owing to appearance of diverse new concepts and an advance in micro processing technology.
In addition to efforts to increase frequency of existing microwave band oscillators, there are attempts to lower the operating frequency to have a terahertz band using optical instruments such as a semiconductor laser or a femtosecond laser. Furthermore, recently, attempts have been made to fabricate a compact size terahertz oscillator.
Among the attempts, there has been developed a method of forming a 3D microstructure having, on a substrate, a plurality of steps using MEMS technology. In particular, to form a plurality of steps on a substrate such as Si wafer, a method has been proposed in which a plurality of mask patterns are sequentially deposited on the substrate and repeatedly etched to remove them to thereby fabricate various step structures.
Meanwhile, there has been proposed another method of multi-stage etching using wafer bonding. Herein, a pre-patterned protection layer is bonded to a first wafer, a second wafer is patterned and etched, and the first wafer is finally etched using the pre-patterned protection layer. However, in case of such a multi-stag etching method, a bottom face thereof is irregularly etched to create a radius of curvature thereon, and an etched wall face is shaped like an alphabet character T.